1. Field of the Invention
This invention relates to the manufacture of hydrogen saturated metallic compounds of enhanced stability and improved calorific yield.
2. State of the Prior Art
Active metal powders are widely used as combustible materials, in the manufacture of solid rocket fuels, explosives, and as high-energy additives to fuels such as gasoline, kerosene, diesel fuel etc. An example is aluminum powder with a specific calorific value of 7,390 kcal/kg. Efforts have been made to increase this calorific yield (bracketed numerals below refer to similarly numbered publications in the attached listing References). Classic chemical methods have led to hydride type compounds with high calorific value. For instance [1]: EQU 3Li AlH.sub.4 +AlCl.sub.3 =3LiCl+4AlH.sub.3
The result is aluminum hydride with a calorific yield of about 9,500 Kcal/kg, widely used in production of solid rocket fuels. A drawback of these conventional materials is their low stability when exposed to atmospheric air. Also, these materials suffer from poor temperature stability, tending to dissociate at temperatures above 105.degree. C., and the cost of their industrial production is high. More stable hydrogenated metal compounds of higher calorific value are needed.
In past efforts to overcome these drawbacks, various physico-chemical methods have been applied in the manufacture of metal hydrides. Molecular hydrogen has been combined with aluminum. This however, requires high pressures, about 10 kilobars, making industrial production complicated and costly [2]. Activated hydrogen, in its monoatomic state, is more promising, resulting in hydrogen-saturated aluminum [3]. It has been shown experimentally that aluminum vapor condensed onto a low temperature base can absorb large quantities of monoatomic hydrogen [5]. While this method resulted in high energy solid combustible material, the resulting product was synthesized in thin films at 77.degree. Kelvin, and dissociated at higher temperatures.
Efforts have also been made to introduce monoatomic hydrogen together with argon into aluminum [6]. Bombardment of an aluminum surface with argon and hydrogen ions resulted in a more stable product, which however was formed as a 10 micron layer on a low temperature base, and removal of this thin layer was not practical for industrial production [7].
Currently known is a method for making metal hydrides characterized by heating, partial dissociation and partial ionization of hydrogen and introduction of activated hydrogen with argon into an aluminum surface, with subsequent fixation of the introduced gases by cooling of the aluminum to a temperature below 77.degree. K. The shortcoming of this method is that once the temperature increases, the compound dissociates and hydrogen separates from the metal.
A continuing need exists for a process by which hydrogenated metal compounds can be made with enhanced stability in contact with atmospheric air and at temperatures above 105.degree. C.